Bartels was nominated to the District Court by Dwight D. Eisenhower on April 20, 1959, to a seat vacated by Robert A. Inch. He was confirmed by the United States Senate on July 28, 1959, and received his commission on July 30, 1959. He assumed senior status on December 31, 1973 and heard cases until his death in Brooklyn, New York in 1997. Among his high-profile cases was the 1989 trial and conviction of Gene Gotti, brother of reputed mafioso John Gotti. He was also the trial judge in the Zvonko Bušić case. At the time of Bartels' death, he was the oldest living federal judge.